Basic life support (BLS) is the level of medical care which is used for victims of life-threatening illnesses or injuries until they can be given full medical care at a hospital. It can be provided by trained medical personnel, including emergency medical technicians, paramedics, and by laypersons who have received BLS training. BLS is generally used in the pre-hospital setting, and can be provided without medical equipment.

Many countries have guidelines on how to provide basic life support (BLS) which are formulated by professional medical bodies in those countries. The guidelines outline algorithms for the management of a number of conditions, such as cardiac arrest, choking and drowning. BLS generally does not include the use of drugs or invasive skills, and can be contrasted with the provision of Advanced Life Support (ALS). Most laypersons can master BLS skills after attending a short course. Firefighter, lifeguards, and police officers are often required to be BLS certified. BLS is also immensely useful for many other professions, such as daycare providers, teachers and security personnel and social workers especially working in the hospitals and ambulance drivers.

CPR provided in the field increases the time available for higher medical responders to arrive and provide ALS care. An important advance in providing BLS is the availability of the automated external defibrillator or AED. This improves survival outcomes in cardiac arrest cases.[1]

Healthy people maintain the CABs by themselves. In an emergency situation, due to illness (medical emergency) or trauma, BLS helps the patient ensure his or her own CABs, or assists in maintaining for the patient who is unable to do so. For airways, this will include manually opening the patients airway (Head tilt/Chin lift or jaw thrust) or possible insertion of oral (Oropharyngeal airway) or nasal (Nasopharyngeal airway) adjuncts, to keep the airway unblocked (patent). For breathing, this may include artificial respiration, often assisted by emergency oxygen. For circulation, this may include bleeding control or cardiopulmonary resuscitation (CPR) techniques to manually stimulate the heart and assist its pumping action.

Bystanders with training in BLS can perform the first three of the four steps.[4]

The AHA-recommended steps for resuscitation are known as DRS CAB:

Check for Danger

Check for a Response

Send for help

C directs rescuers to perform 30 Compressions to patients who are unresponsive and not breathing normally, followed by 2 rescue breaths

A directs rescuers to open the Airway

B directs rescuers to check Breathing but no need to deliver rescue breaths

D directs rescuers to attach an AED as soon as it is available and follow prompts

If the patient is unresponsive and not breathing, the responder begins CPR with chest compressions. Previously, the AHA recommended beginning CPR with rescue breaths. If responders are unwilling or unable to perform rescue breathing, they are to perform compression-only CPR, because any attempt at resuscitation is better than no attempt.

According to the American Heart Association, in order to be certified in BLS, a student take an online or in-person course. However, an online BLS course must be followed with an in-person skills session in order to obtain a certification issued by The American Heart Association.[5]

C-A-B is recommended in the new AHA EU guidelines. Keeping these facts as such follow the sequence introduced by AHA guidelines 2010 recommendations C-A-B should be followed in learning and teaching BLS.

Ensure that the scene is safe.

Assess the victim's level of consciousness by asking loudly and shaking at the shoulders "Are you okay?" and scan chest for breathing movement visually. If no response call for help by shouting for ambulance or EMS and ask for an AED( which is available in offices and building floors).

Assess:* If the patient is breathing normally, and pulse is present then the patient should be placed in the recovery position and monitored. Transport if required, or wait for the EMS to arrive and take over.

If patient is not breathing assess pulse at the carotid on your side for an adult, at the brachial for a child and infant for 5 seconds and not more than 10 seconds; begin immediately with chest compressions at a rate of 30 chest compressions in 18 seconds followed by two rescue breaths in 5 seconds each lasting for 1 second.

If the victim has no suspected cervical spine trauma, open the airway using the head-tilt/chin-lift maneuver; if the victim has suspected neck trauma, the airway should be opened with the jaw-thrust technique. If the jaw-thrust is ineffective at opening/maintaining the airway, a very careful head-tilt/chin-lift should be performed.

Blind finger-sweeps should never be performed, as they may push foreign objects deeper into the airway. This procedure has been discarded as this may push the foreign body down the airway and increase chances of an obstruction.
Continue chest compression at a rate of 100 compressions per minute for all age groups, allowing chest to recoil in between. For adults push up to 5 cm and for child up to 4 cm. For infants up to 3 cm or 1/3 of the chest diameter antero-posteriorly. Keep counting aloud. Press hard and fast maintaining the rate of at about 100/minute. Allow recoil of chest fully between each compression. After every 30 chest compressions give two rescue breaths in adult and child victim, Continue for five cycles or two minutes before re-assessing pulse.

Attempt to administer two artificial ventilations using the mouth-to-mouth technique, or a bag-valve-mask (BVM). The mouth-to-mouth technique is no longer recommended, unless a face shield is present. Verify that the chest rises and falls; if it does not, reposition (i.e. re-open) the airway using the appropriate technique and try again. If ventilation is still unsuccessful, and the victim is unconscious, it is possible that they have a foreign body in their airway. Begin chest compressions, stopping every 30 compressions, re-checking the airway for obstructions, removing any found, and re-attempting ventilation.

If the ventilations are successful, assess for the presence of a pulse at the carotid artery. If a pulse is detected, then the patient should continue to receive artificial ventilations at an appropriate rate and transported immediately. Otherwise, begin CPR at a ratio of 30:2 compressions to ventilation's at 100 compressions/minute for 5 cycles.

After 5 cycles of CPR, the BLS protocol should be repeated from the beginning, assessing the patient's airway, checking for spontaneous breathing, and checking for a spontaneous pulse as per new protocol sequence C-A-B. Laypersons are commonly instructed not to perform re-assessment, but this step is always performed by healthcare professionals (HCPs).
If an AED is available it should be activated immediately and its directives followed and (if indicated), call for clearance before defibrillation/shock should be performed. If defibrillation is performed, begin chest compression immediately after shock.

BLS protocols continue until (1) the patient regains a pulse, (2) the rescuer is relieved by another rescuer of equivalent or higher training (see patient abandonment), (3) the rescuer is too physically tired to continue CPR, or (4) the patient is pronounced dead by a medical doctor.[3]

At the end of five cycles of CPR, always perform assessment via the AED for a shockable rhythm, and if indicated, defibrillate, and repeat assessment before doing another five cycles.

The CPR cycle is often abbreviated as 30:2 (30 compressions, 2 ventilations or breaths). CPR for infants and children uses a 15:2 cycle when two rescuers are performing CPR, but still uses a 30:2 if there is only one rescuer. Two person CPR for an infant also requires the "two hands encircling thumbs" technique for the rescuer performing compressions.

Rescuers should provide CPR as soon as an unresponsive victim is removed from the water. In particular, rescue breathing is important in this situation.

A lone rescuer is typically advised to give CPR for a short time before leaving the victim to call emergency medical services.

Since the primary cause of cardiac arrest and death in drowning and choking victims is hypoxia, it is more important to provide rescue breathing as quickly as possible in these situations, whereas for victims of VF cardiac arrest chest compressions and defibrillation are more important.

In unresponsive victims with hypothermia, the breathing and pulse should be checked for 30 to 45 seconds as both breathing and heart rate can be very slow in this condition.

If cardiac arrest is confirmed, CPR should be started immediately. Wet clothes should be removed, and the victim should be insulated from wind. CPR should be continued until the victim is assessed by advanced care providers.

Rescuers should intervene in victims who show signs of severe airway obstruction, such as a silent cough, cyanosis, or inability to speak or breathe.

If a victim is coughing forcefully, rescuers should not interfere with this process.

If a victim shows signs of severe airway obstruction, abdominal thrusts should be applied in rapid sequence until the obstruction is relieved. If this is not effective, chest thrusts can also be used. Chest thrusts can also be used in obese victims or victims in late pregnancy. Abdominal thrusts should not be used in infants under 1 year of age due to risk of causing injury.

If a victim becomes unresponsive he should be lowered to the ground, and the rescuer should call emergency medical services and initiate CPR. When the airway is opened during CPR, the rescuer should look into the mouth for an object causing obstruction, and remove it if it is evident.

This article is outdated. Please update this section to reflect recent events or newly available information.(November 2011)

Adult BLS guidelines in the United Kingdom were also published in 2005 by the Resuscitation Council (UK),[6] based on the 2005 International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science with Treatment Recommendations (CoSTR) published in November 2005.[7]

They allow the rescuer to diagnose cardiac arrest if the victim is unresponsive and not breathing normally.

Rescuers are taught to give chest compressions in the center of the chest, rather than measuring from the lower border of the sternum.

Rescue breaths should be given over 1 second rather than 2 seconds.

For an adult victim, the initial 2 rescue breaths should be omitted, so that 30 chest compressions are given immediately after a cardiac arrest has been diagnosed.

These changes were introduced to simplify the algorithm, to allow for faster decision making and to maximize the time spent giving chest compressions; this is because interruptions in chest compressions have been shown to reduce the chance of survival.[8] It is also acknowledged that rescuers may either be unable, or unwilling, to give effective rescue breaths; in this situation, continuing chest compressions alone is advised, although this is only effective for about 5 minutes.[9]

Assess the severity of airway obstruction. If the victim is able to speak and cough effectively, the obstruction is mild. If the victim is unable to speak or cough effectively, or is unable to breathe or is breathing with a wheezy sound, the airway obstruction is severe.

If the victim has signs of mild airway obstruction, encourage him to continue coughing; do nothing else.

If the victim has signs of severe airway obstruction, and is conscious, give up to 5 back blows (sharp blows between the shoulder blades with the victim leaning well forwards). Check to see if the obstruction has cleared after each blow. If 5 back blows fail to relieve the obstruction, give up to 5 abdominal thrusts, again checking if each attempt has relieved the obstruction.

If the obstruction is still present, and the victim still conscious, continue alternating 5 back blows and 5 abdominal thrusts.

If the victim becomes unconscious, lower him to the ground, call an ambulance, and begin CPR.